Software defined networking (SDN) is a network architecture where the forwarding plane (sometimes referred to as the data plane) and the control plane, which are conventionally implemented in a single network node, are separated and implemented in two distinct network nodes. Such distinct network nodes may be referred to as a datapath node and a controller node, respectively. An example of an SDN architecture, or specification, is the OpenFlow Switch Specification, version 1.1.0.
Theoretically, by implementing the forwarding function and the control function in different network nodes, multiple relatively inexpensive datapath nodes may be coupled together and controlled by a single controller node, resulting in an overall lower network cost. Another supposed advantage of SDN is that a single controller node can be more easily programmed to implement new network functionality than would be possible by programming multiple conventional network nodes that combine the control plane and the forwarding plane, thereby simplifying the implementation of additional networking functions in the network.
Moving data from source nodes to destination nodes across multiple network nodes involves complex technology, and conventional network nodes implement multiple Operations, Administration, and Management (OAM) functions that permit an operator to resolve problems, monitor the network, and otherwise operate, administer, or manage the network.
Currently, the datapath nodes of a software defined network do not have the intelligence required to implement OAM functions under the control of the controller node. Even if a datapath node is specially programmed to implement an OAM function, doing so runs counter to the notion of SDN, in that the datapath nodes must again become specially programmed on a datapath-node-by-datapath-node basis, which is what SDN desires to avoid.